audio policy: add rules to select audio parameters

Added rules to select most appropriate sampling rate, format and
channel mask from an input or output profile.
Moved mFlags from IOProfile to its base class AudioPort.
Removed bogus mChannelMask member in DeviceDescriptor class.
Improveed dump of dynamic parameters in AudioPort.

Change-Id: Ic09d320386002a8bafee4a28db00b1001a386678